Improvement in forming curved electrotypes



Improvement in Forrrt'i'g Curved Electrotypes.

N0. 130,140, Patentd Aug. 67,1872.

UNITED STATES PATENT OFFICE.

ANSON JUDSON, OF BROOKLYN, NEW YORK, ASSIGNOR TO HIMSELF AND NATHAN S.CLEMENT, OF NORTIIAMPTON, MASSACHUSETTS.

IMPROVEMENT IN FORMING CURVED ELECT'ROTv'PES.

Specification forming part ofLettcrs Patent No. 130,140, dated August 6,1872.

` Specification describin gan ImprovedMethod of Forming CurvedElect-rotypes, invented by ANSON JUDSON, of Brooklyn, in the county ofKings and State of New York.

The purpose of the invention is to avoid the faults due to wrinklingandirregular contraction in the present mode of producing curvedelectrotypes. These electrotypes, it will be understood, are produced onmolds impressed on flat forms and then curved to a large radius to adaptthem for use on a cylinder-press.

In the ordinary method, anv impression having been taken from a flatform in gutta-percha or the like, the extended flat mold is laid acrossa properly-curved metallic bed, and is partially melted by a gradualrise of temperature until its gravity causes it to sink into and conformto the curvature of its support. It is allowed to cool in this curvedcondition, and is afterward immersed in the bath and the.electrotypeproduced with, of course, a corresponding curvature. Thepartial melting to which the mold is subjected in this process is highlyobjectionable. Beside the delay occasioned in the gradual warming andcooling there is a liability and almost a certainty to produce severalWrinkles and irregular contractions at different points. Myimprovedmethod saves time a-nd produces more perfect work. I can by its meansproduce not only letter-press, but even engravings, with a high degreeof perfection and with very great rapidity, with a small outlay forapparatus. I employmechanical force through the intervention of a iuidto compel the straight mold to bend to the curvature of its bed. Thismay be done either by inducing a vacuum underneath or by inducing asurplus pressure of atmosphere or other gas above; or

` the curve may, under proper conditions, be induced by the pressure ofwater or other dense liquid.

The following is a description of what I consider the best means ofcarrying out my invention.

Figure 1 is a vertical section, showing the apparatus ready to curve amold 5 and Fi g. 2 is a vertical section at right angles to the irst.

A is a table adapted to support and allow the ready introduction andremoval of the other parts represented. B is a curved iron plate orremovable shell of suflcient thickness to give stiffness and support tothe delicate material sustained thereby. This piece B may be the same asis ordinarily employed for this purpose.

- (l is a cover or top piece, of iron or other suitable material,adapted to press rml y and make a tight joint upon thepedges of thedelicatelymolded material D, to be described further on.

O is a broad' backing-piece, which may be formed in a continuous plateor more open work,

.or may be formed entirely of one or more simple cross-bars. Itsfunction is to hold down the cover O firmly upon the bed B and theintermediate molded piece D. E E are bolts littingin T-shaped groovesand carrying nuts E', which hold down the whole and liberate themeasily. The flat mold may be formed, in gutta-percha, as usual, it"preferred, but I believe it better to employ wax, ordinary bees-wax,either alone or mixed in ordinary proportions with other materials toform a plastic mass capable of receiving sharp impressions. I back itwith a sheet of stout cartridge or other paper. The wax adheres stronglyand naturally to the paper, and the back of the paper, as also thehollow face of the iron mold B, is coated with anadhesive cement. Theimpression is produced from the dat form (not represented) on the upperface of the delicate wax surface D, in the ordinary manner. The broadsheet of wax, with the paper beneath, is then laid on the hollow bed Band the cover C applied to form a tight t around the edges. The loweredge of the cover C maybe expanded to make a broad bearing, or it may becontracted to make a sharp edge, or there may be several ridges or sharpedges parallel to each other extending around.` The latter constructionis probably preferable, but I believe either will succeed. The mostserious difficulty involved is in forming a tight joint at the ends, soto speak. I esteem it preferable to make the ends with a curved outlinecorresponding to the form which the delicately-molded wax layer is toassume after it has been bent, and to press it down rmly to a bearing byforce in applying the cover and making the joint. The result is adistortion of the plate D along the lines where the edge is thus appliedand pressed down, and this distortion extends a little ways inwardtoward the middle of the mold; but by forming the mold,with a broad edgethis distortion will not extend into the type surface. VThe surfacewhich has received the impression of the type will remain up in a fiator plane condition, or nearly so, while the edges will bepressed downand held air-tight against the supporting-piece B. Having secured thecover by means of the bolts E andl nuts E the bein g employed, (notrepresented,) air is forced in gently through the pipe m, and thepressure over the wax plate D is gradually increased until the yieldingcharacter of the wax and of the paper backing thereon is not sufficientto resist the strain. It yields gradually, and, the air beneath escapingthrough the aperture represented in the bed-piece B, the wax is soonpressed down fairly to the curvature of the latter. The moment thecemented surface at the back of the paper meets the cemented hollow faceof the iron shell B they adhere firmly, and, the pressure being now letoff, the bolts E may be released, the cover G lifted, and the shell B,with its now closely-fitting impressed material Dmay be lifted ofi',from the table A, and the electrotype produced thereon by depositingfrom a solution in the ordinary manner, while the table A receivesanother shell, B, another ilat wax surface, D, with its paper andcement, and again receives the cover C and the blast of air. I esteem itbut little different to leave the bolts E and the cross-bars orother topwork C off, and having fitted the cover C tightly upon the waxedcoat,pressing it down around all its edges, apply the force of an air-pump,or analogous device, to eX- haust the air from below the impressed layerC by exhausting it through the apertures in the shell B. This mode ofoperation allows only a maximum pressure of about fourteen pounds persquare inch, while the other plan is unlimited 3 but it Will ordinarilyrequire much lesspressure than fourteenpounds toinduce the prompt andtrue curvature desired. There is no particular skill or variation of thetreatment required in obtaining the impression from the type surface onthe wax or in the subsequent deposit of the copper coating. I

I do not consider it absolutely essential to success that the backing ofthe plastic layer D shall be formed of paper, or that the cement shallbe applied on both it and the shell B, but I esteem this the preferablemode of working. The backing up and subsequent use of the curvedelectrotypes may be in the ordinary or any suitable manner.

It will be understood that, when used With the plus pressure above, theholes in the curvedv piece B serve to allow the free escape of the airwhich might otherwise be imprisoned below the paper. The bed A should begrooved or rou'ghened to allow its ultimate release. It may bepracticable to allow sufficiently for this escape of air by merelygroovin g or rou ghening the inn er face of the piece B.

I claim as my invention- The within-described method of producing curvedelectrotypes-that is to say, molding from the flat form in wax oranalogous yielding material and forcibly bending it into a curved formby fluid pressure and afterward holdingit in the curved formallsubstantially as herein specified.

In testimony whereof I have hereunto set my name in presence of twosubscribing witnesses.

- ANSON J UDSON. Witnesses:

THoMAs D. STETsoN, ARNOLD HOERMANN.

